Trailers are typically hitched to vehicles using, in the case of passenger vehicles, a trailer hitch that is mounted at the lower rear of the vehicle. The trailer hitch coupling is at a similar height. The vehicle driver must then manipulate the vehicle to align the trailer hitch with the trailer hitch coupling, which is typically disposed at a front of the trailer. When the rear of the vehicle gets close to the front of the trailer, the driver of the vehicle typically cannot see either the trailer hitch or the trailer hitch coupling. Further, when manipulating the vehicle to align the trailer hitch to the trailer hitch coupling, the driver is typically operating the vehicle in reverse.
There are systems that provide guidance to the driver to aid the driver in aligning the trailer hitch with the trailer hitch coupling. There are for example the systems disclosed in US 2013/0226390 for “Hitch Alignment Assistance,” US 2010/324770 for “Trailer Hitch Alignment Device and Method,” US 2009/0040300 for “Removably Mountable, Portable Vision System,” and U.S. Pat. No. 7,777,615 for “System for Assisting the Attachment of a Trailer to a Vehicle.”
These systems do not determine the height of the ball of the trailer hitch. Knowing the height the ball of the trailer hitch can be advantageous in determining whether the ball of the trailer hitch will collide with the trailer hitch coupling of the trailer as the vehicle is backed toward the trailer or if the ball is lower than the trailer hitch coupling so that it will pass under the trailer hitch coupling.